This program of research is designed to explore whether precursor-induced and diet-induced changes in brain synthesis of serotonin and the catecholamine neurotransmitters alter behavioral and physiological functions in rats. The specific brain outputs studied include pituitary hormone secretion (growth hormone and prolactin), blood pressure, pain sensitivity, and sleep. To date, we have observed that tryptophan administration enhances pulsatile growth hormone secretion, and produces apparent analgesia in the flinch-jump test (in rats fed a corn-based diet). We have also noted that tryptophan or tyrosine injections elicit prompt, sizeable reductions in blood pressure in spontaneously-hypertensive rats. All of these effects can be related to the specific transmitter product (5-HT or NE) involved, by experiments involving the use of the amino acid in combination with other pharmacologic agents. We are presently setting up a rat sleep facility, with which to test the effects of tryptophan, and an automated feeding apparatus, with which to monitor 24-hour responses in food intake to the administration of tryptophan or tyrosine. The effects of dietary protein and carbohydrate content (both acutely and chronically) on these brain outputs will be studied.